1. Field of the Invention
This invention relates generally to impedance matching networks and, more particularly, to an impedance matching and RF power splitter device for substantially matching the characteristic impedance from a transmitter to a load impedance of a multi-element directional antenna array of an RF transmission network.
2. Description of the Related Art
A generator, such as a transmitter, for example, is typically designed to operate into a specific impedance of a network. However, a load (e.g., an antenna) that is coupled to the generator usually does not provide the specific impedance in which the generator is designed to operate.
When the impedance of the load and the impedance as seen by the generator are equal, maximum power is transferred from the generator to the load over a transmission line coupling the generator to the load. If a mismatch between the impedances of the load and generator occurs, however, the power that is not transferred to the load will be returned towards the generator through the transmission line. These rearward-traveling waves combine with their respective forward-traveling waves along the transmission line, and because of the phase differences along various positions within the line, causes standing waves in the transmission line by the alternate cancellation and reinforcement of the voltage and current distributed along the transmission line. The larger the standing waves that occur along the transmission line, the greater the mismatch of the impedance of the load that is coupled to the generator.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
One aspect of the present invention is seen in an apparatus for impedance matching a signal generator to a plurality of elements of a multi-element load. The apparatus comprises an outer conductor having an inner surface and an inner conductor positioned within the outer conductor, and having an outer surface. The apparatus further includes a first set of transformation sections for impedance matching a first impedance of the signal generator to a second impedance, and a second set of transformation sections for matching the second impedance to a third impedance of the plurality of elements of the multi-element load. Each of the first and second sets of transformation sections provides a particular separation distance between the inner surface of the outer conductor and the outer surface of the inner conductor to yield a particular characteristic impedance for each of the first and second sets of transformation sections, thereby substantially matching the first impedance to the third impedance.
Another aspect of the present invention is seen in a method for impedance matching a signal generator to a plurality of antenna elements of a multi-element load. The method includes providing an outer conductor having an inner surface and an inner conductor positioned within the outer conductor, and having an outer surface. The method further includes providing a first set of transformation sections for impedance matching a first impedance of the signal generator to a second impedance, and providing a second set of transformation sections for matching the second impedance to a third impedance of the plurality of elements of the multi-element load. The first and second transformation sections provide a particular separation distance between the inner surface of the outer conductor and the outer surface of the inner conductor to yield a particular characteristic impedance for each of the plurality of transformation sections.